The present invention relates to a liquid crystal display device for displaying characters, figures or the like, and particularly to a liquid crystal display device easily manufactured having an excellent visual angle property and an excellent contrast ratio.
In a conventional twisted nematic (hereinafter referred to as "TN") type liquid crystal display device widely used, electrodes are disposed between two opposing substrates and liquid crystal molecules are disposed in the electrodes. The liquid crystal display device displays "white" in which the liquid crystal molecules are parallel to a surface of the substrates when applying no voltage. Once the voltage is applied thereto, the "white" display gradually changes to a "black" display as a result of the liquid crystal molecules changing their directors or orientation vectors to an electric field in accordance with the applied voltage. Such built up behavior of the liquid crystal molecules when applying the voltage makes the visual angle of the TN type liquid crystal display device narrow.
Japanese Unexamined Patent Publication No. 63-106624 (hereinafter referred to as "related art 1") discloses, for example, a method for improving the visual angle property of the TN type liquid crystal display device. According to the related art 1, one pixel has orthogonal rubbing directions with each other in two opposing glass substrates and is divided into plural areas, of a first area and a second area having different rubbing directions from each other. Built up directions of the liquid crystal molecules are made opposite to each other in the first area and in the second area, thereby improving the visual angle. However, the related art 1 divides the pixel into plural areas of the first and the second areas having different rubbing directions from each other by the use of a micro rubbing technique, which leads to an increase in steps.
Japanese Unexamined Patent Publication No. 10-20323 filed by the present inventors (hereinafter referred to as related art 2) discloses a liquid crystal display device which divides each pixel into four areas having different twist directions and built up directions of the liquid crystal from one another by utilizing a nonuniform electric field. According to the liquid crystal display device of the related art 2, a high voltage is applied to a second electrode where a liquid crystal polymer is disposed on an opening of a first electrode on a rear surface of a substrate via an orientation film to lower a voltage of the first electrode therearound, whereby the nonuniform electrical field is produced between the opposing substrates. The nonuniform electrical field divides each pixel into four to build up the liquid crystal molecules therearound.
However, in the liquid crystal display device of the related art 2, a direction of the nonuniform electrical field in producing a divided structure is different from that in displaying an image. Therefore, when displaying the image, the liquid crystal molecules build up in an opposite direction to that in producing the divided structure. At a boundary of the divided structure, disclination is produced which causes a light leak and lowers a contrast.
In the liquid crystal display device of the related art 2, the first electrode configuring a peripheral electrode is a set of a gate electrode and a drain electrode. A potential of such electrodes is not identical (=0V) with that of a counter electrode opposite to the first electrode when displaying the image. Accordingly, the disclination occurs in the divided structure produced where the potential of the first electrode is 0V and the potential of the second electrode is high, because the electrical field in displaying the image is different from that in producing the divided structure.